1989 Vol. 3 No. 2
Cover Note
Abstract:A linear steady model is constructed to investigate the response of the tropical atmosphere to diabatic heating.The basic equations are similar to those used by Gill(1980),but the long-wave approximation is removed and periodic boundary conditions are taken in longitude.According to the features of the underlying surface temperature(including oceans and land),the heat sources(sinks) are given.Using this analytical model,we have simulated the climatological fields of wind and air pressure in the lower layers of the tropical and subtropical atmosphere in summer(June-August) and winter(December-February).The main features of observations are depicted in simulated fields.More+
1989, 3(2): 132-144.
Abstract:A two-level,quasi-geostrophic long-wave model based on spherical coordinates was developed with the explicit part belonging to a low-order model.However,it includes not only diabatic heating,Ekman friction and mountain distribution,but also parameterized forcing effects of transfer properties of transient eddies.Experiment results showed that,due to the introduction of the parameterization of transfer properties of transient eddies,remarkable improvements on characters of low-order model had been obtained.In addition to its economization in calculation and conciseness in physics as in a low-order model,the long-wave model was shown to describe the energetics and angular momentum balance of the atmosphere much more reasonably,and to present the features of zonal mean westerlies and stationary waves much more correctly than the corresponding low-order model.This kind of long-wave model was therefore regarded as suitable for theoretical research and numerical modelling of some aspects of the general circulation of the atmosphere.More+
Abstract:The influence of eddy viscosity on the distribution of subtropical quasi-stationary planetary waves in summer is analysed theoretically.It is found that since the basic flow is very weak,the eddy viscosity may play an important role for the subtropical planetary-scale motion in summer.A linear,quasi-geostrophic,34-level spherical coordinate model is also utilized to calculate the differences of quasi-stationary planetary waves and of quasi-stationary disturbance pattern responding to forcing by topography and heat sources under the different eddy viscosities.The computed results show that the coefficient of eddy viscosity considerably influences the strength of the subtropical planetary-scale circulation in summer.More+
Abstract:Using the operational model(B model) of Beijing Meteorological Center,we do some of numerical experiments of crossing and rounding mountains in all velocity adjustment scheme,and study dynamic effect of Qinghai-Xizang Plateau and Rocky Mountains on lee cyclones.The results show that due to air flow round the Qinghai-Xizang Plateau,divergence is distributed in the shape of confluence which matches cyclogenesis area and cyclonic track in East Asia.In the downstream of the Qinghai-Xizang Plateau,convergence in the upper troposphere restrains cyclone development in the east of China mainland.In North America,air flow primarily crosses over Rocky Mountains.Air is adiabatically cooled when it flows upward in the west flank of Rocky Mountains,while air is warmed when it flows downward in the lee side.The fact is important for the lee cyclogenesis and the lee frontogenesis of Rocky Mountains.Air flow crossing over Rocky Mountains is also the main cause for forming dryline in the mid-west of United States.More+
Abstract:A numerical experiment of squall-line formation has been made with a baroclinic quasi-two-dimensional PE-model.The results show that the latent heat released by cumulus convection plays an important role in the formation of a certain kind of squall-line.In the process of the formation of squall-line,the nonlinear concentration of perturbation is clearly shown.More+
Abstract:In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u*/A(A is the wind speed at the top of PBL) and φ(the angle between winds near the surface and at the top of PBL) of PBL are investigated in which the wind direction at the top of PBL is a periodic function of time but the wind speed at the top of PBL does not change.The u*/A increases and φ decreases when the wind direction at the top of PBL rotates anticlockwise and vice versa.Hence the parameterization of PBL in the large-scale models derived under the stationary condition should be corrected by accounting for the nonstationary process.The similar results are obtained in the numerical solution of the motion equation of PBL.The influences of this nonstationary process on the profiles of the wind in PBL are also analyzed.More+
Abstract:A shower cloud observed in Jiangxi,a hailstorm observed in Hebei and "75.8" torrential rain in Henan are simulated with our microphysical model in a one-dimensional framework.The model,using the radiosonde data as input,gets its output which shows agreement in many aspects as compared with observations in each case.The glaciation of small cumulus cloud,low precipitation efficiency of hailstorm and the persistence of torrential rain are demonstrated.It is also shown that the Bergeron process has little influence,but the warm-rain process plays an important role in the formation of precipitation in cumulonimbus with a warm cloud base.More+
Abstract:This paper describes a two-dimensional slab-symmetric hailcloud model,of which dynamics almost contains all the dynamic factors.The model with the improved precipitation process included can show the biparameter change of particle size-distribution.A new suspending lateral boundary condition is proposed which may improve the influence of boundary on the airflow within computing domain.The subroutines designed for studying the change in outline of precipitating particle region can describe the interaction between airflow and precipitation particles.With this model the structure of weak ccho region in hailcloud is simulated and the airflow patterns under different thermal disturbances and wind shear are studied.More+
1989, 3(2): 212-219.
Abstract:From analysis of observational data of thunderstorms in Gansu,China,it was deduced that the electric structure of thunderclouds in this region is often positive charge in the upper,main negative in the middle layer and another positive charge,large in magnitude and extensive in dimension,in the lower part.Intracloud discharges often take place between the main negative charge and lower positive charge instead of upper.Case analysis of 6 intracloud discharges in two storms on August 3 and 4,1986 shows that the centers of these discharges and the dipole moments destroyed were at the altitude of 3.8-6 km msl(7.6-13.5℃) and 18-40 C km,respectively.More+
Abstract:According to statistical inference method,the asymptotic distributions,concretely,Weibull and Gumbel distributions,for yearly extremes of surface temperature and wind in China were discovered.In this study we used the data of 173 stations for yearly maximum surface temperature and 158 stations for yearly minimum surface temperature and 83 stations for yearly maximum surface wind during the period from 1951 to 1982.Finally,the characteristics of the asymptotic distributions were discussed briefly.More+
Abstract:The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982-1983.The mian results are as follows:The central and northern parts of the Plateau act as heat sinks in winter from November to January.Both eastern and southern parts of the Plateau are of heat sources.In summer,the main part of the Plateau acts as a strong heat source,and the center of the heating field is in the southeastern Plateau.However the main part of the Plateau acts as a heat sink for the atmospheric heating fields from October to March.The maximum intensity of the atmospheric heat sink over the central Plateau appears in December and January.From April to September,the main part of the Plateau acts as a heat source for the atmospheric heating fields.More+
1989, 3(2): 242-249.
Abstract:The turbulent flow in and above plant canopies is of fundamental importance to the understanding of transport processes of momentum,heat and mass between plant canopies and atmosphere,and to microme-teorology.The Reynolds stress equation model(RSM) has been applied to calculate the turbulence in canopies in this paper.The calculated mean wind velocity profiles,Reynolds stress,turbulent kinetic energy andviscous dissipation rate in a corn canopy and a spruce forest are compared with field observed data and with Wilson's and Shaw's model.The velocity profiles and Rynolds stress calculated by both models are in good agreement,and the length scale of turbulence appears to be similar.More+
Abstract:Daily precipitation records for summer months at fourteen stations in Shaanxi Province,China,have been analysed to determine the dependence of daily precipitation occurrence by use of MAICE and MBICE procedures.The results show that dependence is statistically significant at all fourteen stations located in different climatic regions.Fitting of Markov chain models gives a satisfactory description of the distributions of wet and dry sequences,including long-length spells.More+

Vol. 3, No. 2, May 1989
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